1,944 research outputs found
Topological responses from chiral anomaly in multi-Weyl semimetals
Multi-Weyl semimetals are a kind of topological phase of matter with discrete
Weyl nodes characterized by multiple monopole charges, in which the chiral
anomaly, the anomalous nonconservation of an axial current, occurs in the
presence of electric and magnetic fields. Electronic transport properties
related to the chiral anomaly in the presence of both electromagnetic fields
and axial electromagnetic fields in multi-Weyl semimetals are systematically
studied. It has been found that the anomalous Hall conductivity has a
modification linear in the axial vector potential from inhomogeneous strains.
The axial electric field leads to an axial Hall current that is proportional to
the distance of Weyl nodes in momentum space. This axial current may generate
chirality accumulation of Weyl fermions through delicately engineering the
axial electromagnetic fields even in the absence of external electromagnetic
fields. Therefore, this work provides a nonmagnetic mechanism of generation of
chirality accumulation in Weyl semimetals and might shed new light on the
application of Weyl semimetals in the emerging field of valleytronics.Comment: 13 pages, 2 tables, 2 figures, accepted by Physical Review
Renormalization Group Approach to Stability of Two-dimensional Interacting Type-II Dirac Fermions
The type-II Weyl/Dirac fermions are a generalization of conventional or
type-I Weyl/Dirac fermions, whose conic spectrum is tilted such that the Fermi
surface becomes lines in two dimensions, and surface in three dimensions rather
than discrete points of the conventional Weyl/Dirac fermions. The
mass-independent renormalization group calculations show that the tilting
parameter decreases monotonically with respect to the length scale, which leads
to a transition from two dimensional type-II Weyl/Dirac fermions to the type-I
ones. Because of the non-trivial Fermi surface, a photon gains a finite mass
partially via the chiral anomaly, leading to the strong screening effect of the
Weyl/Dirac fermions. Consequently, anisotropic type-II Dirac semimetals become
stable against the Coulomb interaction. This work provides deep insight into
the interplay between the geometry of Fermi surface and the Coulomb
interaction.Comment: Final pulished versio
Autonomous boat dynamics: how far away is simulation from the high sea?
The study demonstrates the process of implementing a 3-degrees-of-freedom surge-sway-yaw boat dynamic model in a numeric simulation environment. Estimated environmental disturbance force introduced in the simulation provides a scope for determining boat thrust force range and thrust angle range. The basic simulation framework allows the designer of a small robotic boat to change control logics in relation to the actuator (thruster) layout without the construction of a prototype. The study draws on the key assumptions of hydrodynamic added masses and damping coefficients, and indicates ways to estimate these parameters. The framework offers a starting point for anyone working on mechanical design of a robotic test boat for developing any control algorithms
A Faster, Lighter and Stronger Deep Learning-Based Approach for Place Recognition
Visual Place Recognition is an essential component of systems for camera
localization and loop closure detection, and it has attracted widespread
interest in multiple domains such as computer vision, robotics and AR/VR. In
this work, we propose a faster, lighter and stronger approach that can generate
models with fewer parameters and can spend less time in the inference stage. We
designed RepVGG-lite as the backbone network in our architecture, it is more
discriminative than other general networks in the Place Recognition task.
RepVGG-lite has more speed advantages while achieving higher performance. We
extract only one scale patch-level descriptors from global descriptors in the
feature extraction stage. Then we design a trainable feature matcher to exploit
both spatial relationships of the features and their visual appearance, which
is based on the attention mechanism. Comprehensive experiments on challenging
benchmark datasets demonstrate the proposed method outperforming recent other
state-of-the-art learned approaches, and achieving even higher inference speed.
Our system has 14 times less params than Patch-NetVLAD, 6.8 times lower
theoretical FLOPs, and run faster 21 and 33 times in feature extraction and
feature matching. Moreover, the performance of our approach is 0.5\% better
than Patch-NetVLAD in Recall@1. We used subsets of Mapillary Street Level
Sequences dataset to conduct experiments for all other challenging conditions.Comment: CCF Conference on Computer Supported Cooperative Work and Social
Computing (ChineseCSCW
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